Schappi et al. 1997. Authors
found that atmospheric Bet v 1 allergen levels were positively correlated with
the amount of airborne birch pollen. However on days with light rain Bet v 1
allergens were present in the atmosphere in respirable-sized
particles when no pollen was registered.
They concluded that the birch pollen count does not completely reflect
the birch allergen load in the air.